1. Field of the Invention
The present invention relates to a radio signal receiving device. More particularly, the present invention relates to a receiving device having an input terminal for inputting an input signal and an output terminal for amplifying the input signal from the input terminal and then outputting the output signal.
2. Description of the Related Art
The conventional radio signal receiving device extracts signals from a predetermined frequency band with low noise by maintaining a band pass filter for filtering the predetermined frequency band from the input signal in a constant temperature. The band pass filter that is made from a superconductor for this object is contained within an insulating container and thereby can be maintained in the constant temperature.
FIG. 1 shows a block diagram of the structure of the conventional radio signal receiving device. The conventional radio signal receiving device includes a band pass filter 10, a low noise amplifier 20, an insulating container 80, a cooling means 40, an input terminal 60, an output terminal 50, a first power line 81, a second power line 82, a third power line 83, a fourth power line 84, a cooling member 44, a temperature sensor 46 and a temperature control heater 48.
Band pass filter 10 filters the frequency band of the input signal from input terminal 60. Insulating container 80 contains band pass filter 10 so that the filter is insulated from the outside. Low noise amplifier 20 amplifies the signal that is filtered by band pass filter 10 and then outputs the amplified signal to output terminal 50. Low noise amplifier 20 is powered from first power line 81 and second power line 82.
Cooling means 40 cools band pass filter 10 to maintain it at a temperature where the filter operates in a superconducting state, using cooling member 44. The power for operating cooling means 40 is supplied from the outside via a power terminal for cooling means 42. A temperature monitor signal showing the temperature of cooling member 44 detected by temperature sensor 46 is outputted from third power line 83. The temperature control signal for controlling temperature control heater 48 mounted in cooling member 44 is inputted from fourth power line 84.
The amplifier connected to the band pass filter is contained in the insulating container together with the band pass filter, thereby reducing heat noise. Thus, it is preferable that the temperature of cooling member 44 is constantly maintained. However, since the conventional radio signal receiving device has heat transfer from first power line 81, second power line 82, third power line 83 and fourth power line 84, it is difficult to maintain the temperature in the insulating container at a constant temperature. Thus, an insulating container, that contains the band pass filter and has higher insulating capability, has been demanded.